JPH1046392A - Anodized aluminum-coated article having metallic luster appearance and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anodized aluminum-coated article having a metallic luster outside face closely resembling a metal such as stainless steel and to furnish its production method. SOLUTION: This anodized aluminum-coated article A is produced by forming an anodic oxide film and an electrodeposited film 3 on an aluminum or aluminum alloy substrate 1 chemically polished with a chemical polishing soln. contg. phosphoric acid and sulfuric acid as the main components. The article A is produced by degreasing, chemically polishing and then anodizing the substrate 1 and then coating the substrate with a water base paint by electrodeposition. An anodized aluminum-coated article having a metallic luster appearance closely resembling a metal such as stainless steel and excellent in durability such as corrosion resistance and weatherability is stably produced at a low cost. Further, the NOX causing environmental pollution are not generated or generated only in a minute amt., the working environment is not contaminated, and the pollution of air and water is remarkably reduced. Besides, since a conventional anodized aluminum coating line is utilized, the investment in equipment is lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alumite-coated article having a metallic luster appearance and a method for producing the same. In detail, even if there are irregularities such as dice marks and scratches on the surface of an aluminum or aluminum alloy base material such as an extruded material or a rolled material, these irregularities can be smoothed, and even if the irregularities remain, they can be less noticeable. The present invention relates to an alumite coated article capable of imparting a metallic luster such as stainless steel or a surface appearance to an aluminum or aluminum alloy substrate and a method for producing the same.

[0002]

2. Description of the Related Art Aluminum or aluminum alloy (hereinafter referred to as "aluminum") is lightweight, has good workability and is excellent in strength, and is anodized to form an anodized film (hereinafter referred to as an alumite film or an alumite film). After forming an anodized layer), the ones that have been sealed or painted have excellent durability such as corrosion resistance and weather resistance, so they can be used for building materials, ships, trains, automobiles, home appliances, electronic devices, Widely used for office equipment, optical equipment, etc. On the other hand, a mirror-finished stainless steel having an excellent metallic luster appearance such as a chrome-plated surface or a nickel-plated surface is used for the same uses as the above-mentioned aluminum substrate. However, stainless steel costs about three times as much as aluminum and about ten times as expensive as aluminum, so there is a demand in the market to substitute stainless steel for aluminum.

[0003]

As an aluminum product having a high reflectivity, an acrylic transparent electrodeposition coating film having a thickness of 2 to 5 μm is formed on an aluminum plate whose surface is mirror-finished by diamond processing. A reflecting mirror and a reflecting plate are known (see Japanese Patent Application Laid-Open No. 1-254901). However, the above reflectors and reflectors have an electrodeposition coating film directly formed on an aluminum plate having a mirror-polished surface, so that the coating film has poor adhesion and poor overall corrosion resistance, so that it is not suitable for outdoor use. It is not suitable. Further, it is extremely difficult to mechanically polish the surface of an aluminum base material having a curved portion, a thin aluminum panel, an extruded aluminum material having a complicated shape, and the like.

[0004] On the other hand, as a method for imparting a performance that can withstand long-term outdoor use to an aluminum substrate, it is known that the aluminum substrate is subjected to anodizing treatment, sealing treatment and / or painting. By this method, it becomes possible to impart excellent durability such as corrosion resistance and weather resistance to the aluminum substrate. Before the above-described anodizing treatment, the aluminum substrate is subjected to a degreasing treatment for removing impurities such as oils and fats on the surface, and further to removing dice marks on the surface, irregularities such as scratches, and naturally occurring oxide films and the like. Is generally subjected to a cleaning process such as an etching process. However, since this cleaned aluminum substrate has a rough surface with surface irregularities remaining, even if this aluminum substrate is anodized and a transparent coating film is further formed on the alumite layer, , Due to irregular reflection of light on the rough surface,
An alumite-coated article exhibiting a metallic-like high gloss appearance cannot be obtained.

The inventor of the present invention has proposed a method of chemically or electrically polishing a cleaned aluminum substrate, anodizing the aluminum substrate, and forming a transparent coating film on the alumite layer. It has been found that an alumite-coated article exhibiting a metallic glossy surface or a mirror surface of stainless steel can be obtained, and has already filed a patent application (Japanese Patent Application Laid-Open No. Hei 7-3429).
No. 2). However, according to the above method, an alumite-coated article exhibiting an excellent metallic luster appearance can be obtained, for example, a die mark on the surface of an aluminum substrate,
When the irregularities such as scratches and minute corrosion are not sufficiently smoothed, the resulting alumite-coated article has a high gloss mirror surface on the aluminum substrate, and conversely, pinholes due to the irregularities and corrosion There was a problem that the value of the product significantly decreased. Further, in the above-described method, since the aluminum substrate to chemical polishing process with a composition containing phosphoric acid and nitric acid as a main component, occurrence of the NO _X gas can not be avoided in this chemical polishing treatment, the aluminum surface treatment line It was necessary to install a large-scale NO _x gas absorption and removal device. Furthermore, there is a pollution problem caused such as pollution and effluent control the working environment by the generation of the NO _X gas.

An object of the present invention is to provide an excellent metallic luster appearance in which, even if irregularities such as dice marks, scratches, minute corrosion, and the like formed on the surface of an aluminum substrate remain, pinholes due to the irregularities and corrosion are inconspicuous. An object of the present invention is to provide an alumite-coated article having: Another object of the present invention is to provide a NO.
_No or very little _X gas is generated, which can greatly reduce the occurrence of pollution problems such as pollution of the working environment and drainage regulations, and install a large-scale NO _X gas absorption and removal device in the treatment line An object of the present invention is to provide a method for producing an alumite-coated article having a metallic luster appearance that is unnecessary.
Another object of the present invention is to provide a method capable of utilizing a conventional aluminum alumite coating line and stably producing an anodized aluminum article having a metallic luster appearance.

[0007]

Means for Solving the Problems The present inventors, in the above-mentioned method was completed earlier, eliminating the nitrate component that generates NO _X gas that is a major obstacle to industrialization from the components of the chemical polishing composition As a result of repeated research focusing on, the polishing effect contains phosphoric acid and sulfuric acid as the main components, which are said to be significantly inferior to the electrolytic polishing treatment and the chemical polishing solution containing phosphoric acid and nitric acid as the main components Surprisingly, even if irregularities such as dice marks, scratches, minute corrosion, etc. remain on the surface of the aluminum base material, the use of the chemical polishing liquid makes the irregularities less noticeable and deep, calm stainless steel. It has been found that an alumite-coated article having a metallic luster appearance such as that described above can be obtained. The present invention has been completed based on the above findings.

That is, the alumite-coated article having a metallic luster appearance of the present invention has an anodized film and an electrode on the surface of an aluminum substrate which has been chemically polished with a chemical polishing solution containing phosphoric acid and sulfuric acid as main components. The coating film is formed. Further, in the method for producing an alumite-coated article having a metallic luster appearance of the present invention, an aluminum substrate was immersed in a chemical polishing solution containing phosphoric acid and sulfuric acid as main components, subjected to chemical polishing, and then anodized. Thereafter, the water-based paint is electrodeposited.

FIG. 1 is a schematic sectional view showing the structure of an alumite-coated article having a metallic luster appearance according to the present invention. In the figure, A is an alumite-coated article having a metallic luster appearance. An alumite layer 2 is formed on both surfaces of an aluminum substrate 1, and an electrodeposition coating film 3 is formed thereon. Reference numeral 5 denotes a surface subjected to chemical polishing, which indicates the surface of the alumite layer 2.

The aluminum substrate 1 includes, for example, building materials such as window frame materials, panels, poles, and the like.
Materials made of various shapes of aluminum or aluminum alloy used for various applications such as vehicles such as ships, trains and automobiles, electric products, electronic devices, office devices, optical devices, and the like. The type of the aluminum alloy is not particularly limited, but a higher purity aluminum alloy is preferable because the gloss of the anodized aluminum article is excellent. It is preferable to use an aluminum alloy such as an Al-Mg-based, Al-Mg-Si-based, or Al-Zn-Mg-based alloy to which a small amount of Mg is added because a high gloss surface can be obtained. As the aluminum base material, base materials having various shapes such as a plate material, a shape material, and a rod material formed by rolling or extrusion can be suitably used. Further, an aluminum substrate having a curved portion such as a bent portion or a round portion can also be suitably used.

In the present invention, it is important that before the anodic oxidation treatment, the surface of the aluminum substrate is subjected to a chemical polishing treatment with a chemical polishing liquid containing phosphoric acid and sulfuric acid as main components. By performing the chemical polishing treatment using this specific chemical polishing liquid, the base surface of the aluminum base material is smoothed.

The alumite layer 2 is formed on the aluminum substrate 1 which has been smoothed by the chemical polishing treatment.
In the present invention, the thickness of the alumite layer is not particularly limited, but when the alumite-coated article is used indoors, for example, less than 6 μm, preferably 0.1 to 5 μm
It is appropriate that the film thickness is of the order of magnitude. On the other hand, when the alumite-coated article is used outdoors, it is appropriate to set the film thickness to 6 μm or more, preferably about 7 to 20 μm. The alumite layer 2 may be colored with a dye or a pigment, or colored to a desired color by a known method such as an inorganic electrolytic coloring method.

The electrodeposition coating film 3 is formed by applying an aqueous coating on the alumite layer 2 by electrodeposition. Since the electrodeposition coating is excellent in throwing power, the electrodeposition coating is uniformly formed on the alumite layer 2. The electrodeposition coating film 3 may be a colorless and transparent coating film or a transparent or translucent coating film colored in a desired color. Although the thickness of the electrodeposition coating film 3 is not particularly limited, when the alumite-coated article is used indoors, for example, 7
It is appropriate that the film thickness is less than μm, preferably about 1 to 6 μm. On the other hand, when the alumite-coated article is used under severe outdoor conditions, it is appropriate that the film thickness is 7 μm or more, preferably about 7 to 20 μm.

The alumite-coated article A having the above metallic luster appearance is produced, for example, by the following method.
FIG. 2 is a process diagram showing a manufacturing process of an alumite-coated article having a metallic luster appearance. Hereinafter, each step will be described in detail.

(1) Degreasing treatment step: First, a known degreasing method such as solvent degreasing, alkali degreasing, surfactant degreasing or emulsion degreasing, electrolytic degreasing, etc., is performed on the aluminum substrate. By this degreasing treatment, fats and oils adhering to the aluminum base material surface are removed.

(2) Chemical polishing treatment step: After sufficiently washing the degreased aluminum substrate with water, it is placed in a chemical polishing liquid containing phosphoric acid and sulfuric acid as main components and heated to 90 to 120 ° C. for 5 seconds. Soak for about 180 seconds. As the chemical polishing liquid used in the chemical polishing treatment, any specific chemical polishing liquid containing phosphoric acid and sulfuric acid as main components and nitric acid of 3% by weight or less may be used. As such a chemical polishing liquid,
For example, phosphoric acid 60 to 80% by weight, sulfuric acid 10 to 20% by weight, nitric acid 0 to 3% by weight, metal ion 0.005 to 1% by weight, gas inhibitor 0.1 to 2% by weight, etching inhibitor 0.1 A composition comprising about 2% by weight and the balance of water can be used. By this chemical polishing treatment, the surface of the aluminum base material is smoothed and has a metallic luster.

(3) Anodizing treatment step: The above-mentioned chemically polished aluminum substrate is sufficiently washed with water and then immersed in a known electrolytic solution such as sulfuric acid, phosphoric acid, oxalic acid, etc., and this is used as an anode. And a DC and / or AC voltage is applied between the two electrodes. In this anodic oxidation treatment, generally used anodic oxidation conditions can be directly applied to the solution temperature, electrolysis voltage, current density, electrolysis time and the like. Since the film thickness of the alumite layer varies depending on the type of the electrolytic solution and the above-described anodic oxidation conditions, in the present invention, appropriate conditions for obtaining a desired film thickness may be selected and used. By this anodizing treatment, a uniform alumite layer is formed on the surface of the aluminum substrate smoothed by the chemical polishing treatment.

In the present invention, a water washing step is essential after the above-mentioned anodizing treatment.
Hot water washing treatment, sealing treatment and the like can be performed. As the coloring treatment, known methods such as dyeing with a dye, coloring with an organic or inorganic pigment, and inorganic electrolytic coloring for electrically depositing a metal in micropores of the alumite layer can be applied. Also,
As the sealing treatment, known methods such as steam sealing, hot water sealing, and sealing with a sealing agent can be applied. However, since the electrodeposition coating is applied in the next step, this sealing treatment is to complete the imperfect sealing such that electrical conduction is possible.

(4) Electrodeposition step After sufficiently washing the anodized aluminum substrate with water, it is used as an anode or a cathode in an aqueous paint capable of electrodeposition (hereinafter referred to as an electrodeposition paint). It is immersed, and a DC and / or AC voltage is applied between it and the counter electrode. As the electrodeposition paint used for the electrodeposition coating, an anionic or cationic thermosetting water-based paint, specifically an acrylic,
A water-soluble or water-dispersible resin paint such as an epoxy-based, polybutadiene-based, or fluorine-based resin can be suitably used. By this treatment, a transparent electrodeposition coating film is formed on the aluminum substrate subjected to the anodic oxidation treatment.

In the present invention, an electrodeposition paint can be used in which a small amount of a dye or pigment is contained so that a transparent or translucent colored electrodeposition coating film can be formed by electrodeposition coating. Further, after anodizing the aluminum base having a curved portion such as a bent portion or a radius portion, and then performing electrodeposition coating, the electrodeposited coating film is cured by heating. It is easily deformed and its curvature changes. If this deformation is corrected mechanically, cracks will occur in the alumite layer, or the scale will have a scaly appearance, making it difficult to obtain a metallic luster appearance. In such a case, for example, the coating film curing temperature is 180 ° C.
Hereinafter, it is recommended to use a low temperature crosslinking type or room temperature crosslinking type electrodeposition coating material having a temperature of preferably 150 ° C. or less. It is also recommended to use a UV-curable or radiation-curable electrodeposition coating that does not require heat curing.

In the above-mentioned electrodeposition coating, the thickness of the coating film depends on the type and the liquid temperature of the water-based coating used, the voltage at the time of electrodeposition coating,
It changes depending on the electrodeposition conditions such as the distance between the electrodes, the electrode area ratio, and the energization time, but is usually controlled by the energization time under general electrodeposition conditions. For example, when an acryl-melamine-based electrodeposition paint is used, the liquid temperature is 15 to 25 ° C., the applied voltage is 100 to 300 volts, and the electrode area ratio is 1: 1: anode: cathode.
When a direct current is applied for 0.5 to 5 minutes under the condition of 1-1: 2, an electrodeposition coating film of about 2 to 30 μm can be formed.

(5) Coating Curing Step After the electrodeposition coating, the aluminum substrate is subjected to a heat treatment at 50 to 300 ° C. for about 10 to 60 minutes, usually with or without water washing. By this heat treatment, the coating film melts,
The resin is cured by three-dimensional crosslinking, and a uniformly smooth coating film is formed on the surface of the aluminum substrate. In the above-mentioned electrodeposition coating step, when a room temperature-curable electrodeposition coating is used, it may be left at room temperature. When using an ultraviolet-curable or radiation-curable electrodeposition paint, the respective curing conditions may be used.

[0023]

When an aluminum substrate is chemically polished using a specific chemical polishing solution containing phosphoric acid and sulfuric acid as main components, a soluble salt produced by a chemical reaction becomes thick and convex on the surface of the aluminum substrate. , The dissolution of the concave portions is suppressed, and the dissolution of the convex portions is selectively performed, so that the surface of the aluminum substrate is smoothed. The chemical polishing capacity of this specific chemical polishing liquid is inferior to that of general electrolytic polishing or chemical polishing liquids containing phosphoric acid and nitric acid as main components, so that the surface of the aluminum base material has a high gloss like a mirror surface. Although not obtained, sufficient metallic luster appearance is ensured, and even if there are irregularities on the smooth surface, the irregularities are less noticeable because the periphery is not high gloss. In addition, since the surface of the aluminum base material is not high-gloss, such as a mirror surface, it has a deep, calm metallic gloss appearance. Further, a transparent or translucent colored electrodeposition coating film formed on a colored alumite layer can form various metallic luster appearances in which both colors are combined. In addition, since the aluminum substrate surface has an alumite layer and a uniform electrodeposition coating formed thereon, even when used under severe conditions exposed to the atmosphere by those composite layers,
Shows excellent performance such as corrosion resistance and weather resistance.

Further, according to the method for producing an alumite-coated article having a metallic luster appearance of the present invention, a phosphoric acid and a sulfuric acid which do not contain a nitric acid component or are small amounts of less than 3% by weight are contained as main components. Since a specific chemical polishing liquid is used, NO _X gas is not generated or is extremely small even if it is generated in the chemical polishing process of the aluminum base material. In addition, since the above-mentioned specific chemical polishing liquid is easy to manage, even if the aluminum base material is continuously subjected to chemical polishing treatment, the chemical polishing action is stably exhibited.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings. Note that the present invention is not limited to these examples. Example 1 FIG. 1 is a schematic cross-sectional view showing a configuration of an alumite coated plate having a metallic luster appearance according to an example of the present invention. In the figure, A is an alumite electrodeposition coated plate having a metallic luster appearance. An alumite layer 2 is formed on a chemically polished surface 5 of an aluminum plate 1, and a transparent electrodeposition coating film is formed on the surface thereof. 3 are formed.

The alumite electrodeposition coated plate A was manufactured by the following method. The surface of an aluminum plate (material A6063) measuring 30 cm in length and 5 cm in width is buff polished, then subjected to acetone degreasing treatment, and then heated to a bath temperature of 100 ° C. and contains 80% by weight of phosphoric acid and 20% by weight of sulfuric acid as main components. Chemical polishing liquid consisting of ions, gas inhibitor, etching inhibitor, and water (trade name: Clean Bright #
800 manufactured by Rin Kagaku Kogyo Co., Ltd.) for 60 seconds. After thoroughly washing the aluminum plate with pure water, it was immersed as an anode in a sulfuric acid aqueous solution (170 g / l) at 20 ° C., and a DC voltage of 1 A / dm 2 was applied between the aluminum plate and the counter electrode.
By applying the voltage for 5 minutes, an alumite layer having a thickness of 5 μm was formed. Then, after sufficiently washing the aluminum plate with pure water, an acryl-melamine-based electrodeposition paint (trade name: Honeylight AL800-N manufactured by Honey Chemicals Co., Ltd.) adjusted to 20 ° C;
The resin was immersed as an anode in a resin solid content of 8% by weight, and a voltage of 150 volts was applied between the electrode and a stainless steel plate as a counter electrode, and a direct current was applied for 3 minutes. After the completion of the electrodeposition coating, the electrodeposition coating was physically washed with pure water to remove the physically adhered electrodeposition coating.
Heat treatment was performed in a heating furnace at 30 ° C. for 30 minutes. As a result, an alumite electrodeposited plate having a transparent electrodeposition coating film of about 7 μm on the surface was obtained. This anodized alumite coated plate had a metallic luster appearance.

Example 2 In Example 1, the aluminum plate on which the alumite layer was formed was placed in a nickel coloring bath (Ni: 100 g / l) at 20 ° C.
, An aqueous solution adjusted to pH 4.3 with boric acid), an aluminum plate is provided at the counter electrode, an alternating current electrolytic treatment is performed at 20 volts for 60 seconds, and the alumite layer colored in a light bronze color is formed. After washing, wash thoroughly and then 7
An anodized anodized plate was obtained in the same manner except that the plate was immersed in pure water adjusted to 5 ° C. for 5 minutes, and further washed with pure water. This anodized alumite coated plate had a metallic luster appearance very similar to stainless steel.

Example 3 In Example 2, the aluminum plate on which the alumite layer was formed was subjected to an AC electrolytic treatment in a nickel coloring bath for 1 hour.
An anodized electroplated plate was obtained in the same manner except for 80 seconds. This anodized alumite coated plate had a metallic luster appearance very similar to bronze.

Comparative Example An alumite electrodeposited plate was obtained in the same manner as in Example 1 except that the polishing treatment was changed to the following. Comparative Example 1: Instead of chemical polishing, electrolytic polishing was performed under the following conditions. Phosphoric acid 7 adjusted to a liquid temperature of 80 ° C
In an electropolishing solution consisting of 5% by volume, 4.7% by volume of sulfuric acid, 6.5% by volume of chromic anhydride and the balance being water, the aluminum plate was subjected to a voltage of 10 volts and a current density of 1000 A / m.
2 for 5 minutes. Comparative Example 2: An aluminum plate was immersed for 2 minutes in a chemical polishing treatment liquid consisting of 50% by volume of phosphoric acid, 5% by volume of nitric acid, and the balance being water, which was adjusted to a liquid temperature of 100 ° C., to perform a chemical polishing treatment.

[Comparative Test] A comparative test of the appearance and performance of the alumite electrodeposited coated plates manufactured by the methods of Examples 1 to 3 and Comparative Examples 1 and 2 was performed, and the results are as shown in Table 1. In this comparative test, an aluminum plate whose surface was scratched with a cutter knife to a length of 5 cm after buffing was used. (Judgment of Appearance) The appearance of metallic luster and the easiness of scratches of each anodized electroplated plate were visually judged. In addition, the visual judgment was 5 males and 5 females in the 20-year-old range, 5 males and 5 females in the 30-year-old range, and 5 males and 5 females in the 40-year-old range.
The average value of a total of 30 persons was shown. Metallic luster appearance: ○: Excellent metallic luster, △: Metallic luster, ×
... Inferior in metallic luster. Easiness of scratches: ○: scarcely conspicuous, Δ: scratches slightly conspicuous, ×: scratches conspicuous. (Performance test) Each anodized anodized painted plate was subjected to JIS H-
The corrosion resistance and the coating film adhesion test were performed by the method specified in 8602.

[0031]

[Table 1]

As is clear from Table 1, the anodized electrodeposited plates of Examples have excellent metallic luster appearance, are not easily scratched, and have excellent properties such as corrosion resistance and coating film adhesion. Met. In addition, the anodized electroplated plate of Example 3 exhibited a deep bronze tone.

[0033]

As described above, in the method for producing an alumite-coated article having a metallic luster appearance according to the present invention, the surface of an aluminum substrate is subjected to a chemical polishing treatment with a specific chemical polishing solution, followed by anodizing treatment and then electrodeposition. Since it consists of a series of steps for applying a color coating, a conventional anodized anodizing line can be used as it is. Therefore, an alumite-coated article having a metallic luster appearance can be efficiently manufactured. Further, since a chemical polishing treatment tank may be added to a conventional alumite electrodeposition coating line, equipment costs can be reduced. Further, since a specific chemical polishing liquid containing no nitric acid component or a small amount of less than 3% by weight is used in the chemical polishing treatment, no NOx gas is generated. Even if it occurs, the amount is very small. For this reason, there is no occurrence of pollution problems such as contamination of the working environment in the production line and regulation of drainage, and the health of workers can be maintained. Further, the installation of a device for absorbing and removing the NOx gas is unnecessary or can be simplified, and the equipment cost can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of an alumite-coated article having a metallic luster appearance of the present invention.

FIG. 2 is a process diagram showing a process for producing an alumite-coated article having a metallic luster appearance of the present invention.

[Explanation of symbols]

 A Alumite-coated article having metallic luster appearance 1 Aluminum substrate 2 Alumite layer 3 Electrodeposited coating film 5 Chemically polished surface

[Table 1]

Claims (10)

[Claims] 1. A metallic luster comprising an anodized film and an electrodeposited film formed on a surface of an aluminum or aluminum alloy substrate chemically treated with a chemical polishing solution containing phosphoric acid and sulfuric acid as main components. Anodized anodized articles with appearance. 2. An anodized aluminum article having a metallic luster appearance according to claim 1, wherein the anodic oxide coating is colored. 3. The alumite-coated article having a metallic luster appearance according to claim 1, wherein the electrodeposition coating film is transparent or colored and transparent or translucent. 4. An aluminum or aluminum alloy substrate is immersed in a chemical polishing solution containing phosphoric acid and sulfuric acid as a main component, chemically polished, and then anodized, followed by electrodeposition of a water-based paint. A method for producing an alumite-coated article having a metallic luster appearance characterized by the following. 5. A method for producing an alumite-coated article having a metallic luster appearance, wherein the chemical polishing liquid is a composition containing phosphoric acid and sulfuric acid as main components and nitric acid of 3% by weight or less. 6. The method for producing an alumite-coated article having a metallic luster appearance according to claim 4, wherein the chemical polishing liquid contains an etching inhibitor. 7. The chemical polishing liquid contains 60 to 80% by weight of phosphoric acid, 10 to 20% by weight of sulfuric acid, 0 to 3% by weight of nitric acid, 0.005 to 1% by weight of metal ion, and 0.1 to 2% of gas inhibitor. The method for producing an alumite-coated article having a metallic luster appearance according to claims 4 to 6, wherein the composition is a composition consisting of 0.1% by weight, 0.1 to 2% by weight, and the balance water. 8. The chemical polishing treatment is carried out by removing 9
The method for producing an alumite-coated article having a metallic luster appearance according to claim 4, which is performed by immersing the article in a chemical polishing solution at 0 to 120 ° C for 5 seconds to 180 seconds. 9. The method according to claim 4, wherein the anodized aluminum or aluminum alloy substrate has been subjected to inorganic electrolytic coloring in an aqueous metal salt solution. 10. The method for producing an alumite-coated article having a metallic luster appearance according to claim 4, wherein the water-based paint contains a coloring agent.